This laboratory has been working towards characterizing the possible receptor mechanisms responsible for the therapeutic and side effects of the estrogenic component of the oral contraceptives. Recently we have found a high affinity estrogen specific binding protein in the mammalian liver. We are currently studying its properties to establish if this seems to be an estrogen receptor. An estrogen receptor in liver might contribute to estrogen produced contraceptive side effects by changing the hepatic synthesis of selective plasma proteins (e.g., thrombosis might be potentiated by increases in blood clotting factors and a decrease in the clotting inhibitor antithrombin III) and by changes in other aspects of liver function (e.g., cholesterol gallstone formation may be potentiated by decreased synthesis of bile acids). We are studying: 1) the biochemical properties of the estrogen binding protein in liver; 2) its development with sexual maturation in the rat; 3) regulation of receptor binding; 4) translocation of the receptor from the cytosol to the nucleus in vitro and in vivo; 5) correlation of estrogen binding and estrogen hepatic responses. BIBLIOGRAPHIC REFERENCES: Eisenfeld, A.J., Aten, R., Weinberger, M., Haselbacher, G., and Halpern, K. (1976). Estrogen receptor in the mammalian liver. Science, 191, 862-865. Haselbacher, G., and Eisenfeld, A.J. (1976). Macromolecular binding of estradiol by nuclei in a cell-free system. Biochemical Pharmacology, 25, 2571-2581.